Squashed commit of the following:

libc/semaphore:  Add nxsem_getvalue() which is identical to sem_getvalue() except that it never modifies the errno variable.  Changed all references to sem_getvalue in the OS to nxsem_getvalue().

    sched/semaphore:  Rename all internal private functions from sem_xyz to nxsem_xyz.  The sem_ prefix is (will be) reserved only for the application semaphore interfaces.

    libc/semaphore:  Add nxsem_init() which is identical to sem_init() except that it never modifies the errno variable.  Changed all references to sem_init in the OS to nxsem_init().

    sched/semaphore:  Rename sem_tickwait() to nxsem_tickwait() so that it is clear this is an internal OS function.

    sched/semaphoate:  Rename sem_reset() to nxsem_reset() so that it is clear this is an internal OS function.

wireless/pktradio/pktradio_metadata.c

@@ -120,7 +120,7 @@ void pktradio_metadata_initialize(void)
 
       /* Initialize the mutual exclusion semaphore */
 
-      sem_init(&g_metadata_sem, 0, 1);
+      nxsem_init(&g_metadata_sem, 0, 1);
       g_metadata_initialized = true;
     }
 }